Electrical time delay means



Feb.23,1943.- Q a .5, FREEMAN 2,312,033

ELECTRICAL TI-ME DELAY MEANS Filed July 5, 1941 INVENTOR l .6. 5; P. FREEMAN BYyg 20-A /wrH// ATTORNEY Patented Feb. 23, 1943 ELCTRICAL DELAY i H George Stanley Percival Freeman, Hammersmith, London, England, assignorto Electric & litiasi-V cal industries Limited, Hayes, Middlesex, land, a company of Great Britain Engappiicantm my 5, ian, senti No. @man in creat Britain 4etai iz, este r l Claims.

The present invention relates to electron discharge devices, and electric circuit arrangements including such devices.

'I'he object of the invention is to provide an arrangement operating with electron discharge in which the transit time of electrons in the discharge is large and readily controllable. Such arrangements may be employed, for example, to provide a time delay for signals.

'I'he invention also provides novel electron discharge devices.

According to the present invention, an electric circuit arrangement for operation with electron discharge wherein, in operation, the discharge is produced within a strong magnetic field and takes place throughV an electrostatic deecting eld, is provided, said arrangement including electron reecting means which cause electrons in said discharge to pass repeatedly through said deilecting eld whereby the length Aoi the path of said discharge and the transit time of said electrons is increased. In the case where an arrangement accordingto the invention is utilised as a time delay for signals, the arrangement may comprise means for modulating said discharge in accordance with signals to be delayed and an anode for receiving said discharge connected in an output circuit into which said signals are repeated with the desired delay; Anarrangement according to the inventioncan also be employed for mixing signals with desired delays. In this case an arrangement is used in which, in operation, a plurality of similar discharges are produced, each discharge being modulated in accordance with one of the trains of signals to be mixed and the discharge collecting anode, electrons proceed from said cathode under constraint by said magnetic eld, pass between said deiecting electrodes towards one reiiecting electrode and are deflected by the electrostatic deflecting eld between said deecting electrode, said electrons then being retarded by said reflecting electrode and returned through said deecting iield towards the other reflecting electrode, and again retarded and returned through said deecting field, the electrons being caused to pass through said deecting eld repeatedly and finally emerging therefrom and being constrained by said magnetic field to impinge on said collecting anode.

In order that the said invention may be clearly understood and readily carried into e'ect. the same will now be more fully described with .reference to the accompanying drawing, in

Figure 2 is a diagrammatic side view of a modified pair of electrodes in a device in accordance with the invention, and

Figures 3 and 4 are diagrammaticplan views of electrode arrangements in vfurther lembodiments of the invention. In each of the figures of the drawing like like parts are indicated by the same reference numerals.

currents being combined in a common output l circuit to mix the signals by which said discharges are modulated, said signals being delayed with respect to each other in accordance with .the electron transit times in said discharges. i

In the preferred form of the invention a discharge device adapted to be operated to produce an electron discharge with large transit time is provided, including a cathode `from winch is derived, in operation, an electron stream, a pair of deecting electrodes, reiiecting electrodes arranged one at each end of said deecting electrodes, and a collecting anode, the arrangement being such that in operation if a strong magnetic ield is maintained about said Referring to Figure 1 of the drawing', it will be seen that the arrangement therein shown includes a cathode ray gun I adapted, in operation, to eject a beam of electrons axially and to permitthe projected beam to be modulated electrodes and suitable potentials with respect to said cathode are applied to said defiecting electrodes, said reecting electrodes and said necting electrodes 2, 3. Substantially diagonally of the deiecting elecshaped electrode 4, termed a reflecting electrode, I .which extends at right angles to the deflecting electrodes. A further reflecting electrode E, similar to the electrode 4, is arranged at the same end of the deflecting plates 2, 3, as the gun I opposite the electrode 4, but slightly staggered therefrom or otherwise disposed or formed so as not to interfere with the emission of electrons from thegun I` into the space between the devthe electron gun I and electrodes 2 to 6, inclusive, is immersed in a uniform magnetic field having a direction indicated by the a110W,'v H. this field being strong, that is to say, such as will cause electrons projected into it to proceed in a spiral path of small radius. The deflecting electrodes 2 and 3 are maintained at potentials such that a satisfactory deflecting field isset up between them and their mean value of the potentials is higher than that of thel potential of the cathode of the gun l and is preferably equal to that of the final anode of the gun I. The potential difference between the electrodes 2, 3, can be quite small, for example, such that the potential gradient between the plates is less than `one volt per centimetre. The electrodes It and '5 are maintained at a potential equal to or slightly negative with respect to the potential of the cathode of gun I. The anode 6 is maintained at a potential such that it will collect electrodes emitted from the gun I and may conveniently be connected through a suitable loaf to the iinal anode of the gun.

A typical track P of electron emitted from the gun I is indicated in dotted lines. It will be seen from this that electrons emitted from the gun I are constrained to move parallel to the magnetic field H until they enter the electrostatic deiiectfA ing field between the deflecting electrodes 2 and 3. In the deiiecting field the electrons are deiiected at right angles to the defiecting field and to the magnetic eld H parallel to the deflecting electrodes 2 and 3, so that the track P becomes inclined as shown in the drawing. After emerging from the deecting eld the electrons continue to move with a direction generally parallel to that of the field H towards the reecting electrode 4, which electrode causes the electrons to be reflected back into the deflecting eld to undergo a further deflection in the same direction as before. After re-passing through the deflecting field the electrons approach the reflecting v electrode in a direction parallel to the magnetic field H1 and are again reflected and re-enter thedeflecting field. 'Ihe electrons thus pass to-andfro between the electrodes 4 and 5 undergoing deflection at each passage through the deflecting field until finally the electrons emerge on the collecting anode 6.

In this connection it must be borne Iin mind that the use of crossed magnetic and electrostatic flelds brings about forces which cannot be combined linearly, but must be combined vectorially. As a result, as is well known from the fundamental behavior of electrons, the force acting on the electron must always be at right relatively strong and the electrostatic field is' relatively weak, the electrons follow-' path as indicated in Figures ,1, -3 and4. The electronsin following such a. path, as for example in Figure 1 along the line P, may actually rotate about the line P as an axis, since the presence of the elec-k tromagnetic field prevents radial dispersion of the electrons. This effect is well known in the art, and has been described in the literature, as for example in the paper entitled The Orthicon--A television pick-up tube by Rose and Iams, RCA Review, vol. 4, #2, October, 1939, pp. 186-199, where the action of the lcrossed fields on electrons'is described in detail (see especially pages 193-195) The time taken by the electrons to travel between the gun I and electrode 6 will be dependent mainly on the strength of the deflecting field between the electrodes 2', 3. This will be readily appreciated from the following discussion.

Thus, assuming that the potential of the region in which the electrons move between the deflecting electrodes 2 an'd 3 is the same as that of the final anode of the gun l and the collecting electrode 6, then the electrons will be projected from the gun l with a velocity v, sayl and will move with this velocity through the deiiecting field 'between electrodes 2, 3, to the right-hand end thereof. In this region the electrons will be subject to a retardation due to the field of the reecting electrode v4 which will bring the electron velocity to zero, and subsequently the electrons will be caused to return into the deflecting field, regaining a 4velocity of magnitude v, but in a reverse sense from that with which the electrons were projected initially. If d is Ithe separation between the final anode of `the electron gun I and the left-hand end of, electrodes 2, 3, and also between electrode 4 or 5 and the adjacent ends Likewise, the time taken to travel between the I two reecting electrodes is given by:

'Also, if the collecting" anode 6 is at the same potential as the final anode of gun I and isthe same plane as electrode 4, as shown in Figure 1, the time taken for an electron to travel between reflecting electrodes 4, 5, and collecting anode 6 will be l-l-3d Thus, if an electron-makes N traversals through the deiiecting iield, the time occupied will be approximately 42,3 +(N A 2)(ll;4d +l+3d=N(l -l4d) 2d A v u However, N will be determined by' the rate 6i.

deflection (6) of the beam in the deflecting eld, It can be shown that 9 is proportional to E/H where E is the potential difference between elec` trodes 2 and 3. Thus, we may write:

where K is a constant. The deflectioniwliih -takes place duringeach traversal of an electron n l .mi 21% eIN'CJ K. El Putting-this value for N, we have that the time occupied by an electron in passing from the gun I to the collecting electrode 6 will be The quantity T will represent the time delay ob tainable in the device.

From the above expression for the time delay,

it will be seen that if the term Zd/v issmall compared with the other term in the expression, the time delay T is proportional to H/E. If the electron stream traverses the deiiecting eld a few times the term Zd/v can in fact, usually be ignored. Thus, if as is normally the case, H is constant, the time delay which can be -obtained with the device will be inversely proportional to the potential diierence between the deecting electrodes. It is thus possible to control the' time delay obtained in the device merely by adjusting the aforesaid potential difference. 1 Moreover, the time delay will be rehatively great when the potential diierence between the d eilecting electrodes is small.

Thel magnetic eld H is preferably adjusted so that the electrons enter and leavelthe defleoting iield without, say, tendency to spreadf This phenomenon is discussed, for example, in the specification of United States Patent No. 2,213,- 175. If desired, the deecting electrodes d, 5,l .can be curved, or other expedients adopted as described'in the aforesaid specification.

It may be desirable in some cases te separate the electron gun and the collecting electrode from the reflecting electrodes c and 5 more wide- 50 ly than is done in the arrangement shown in Figure l. Thus, for example, in the pair of deflecting electrodes I2 and I3 .shown in Figure 2, the gap existingbetween the electrodes is made less in the region of thegun I and the collecting electrode 6, the dilecting plates being bent so that their edge portions N are brought together while their middle portions remain relatively widely spaced. With this arrangement the deflection of the electron stream ,is eected' at a greater rate at the regions where it enters the deflecting i'leld than at other parts of the de,- ectingfield so that the `deflections occurring during the initial and final traversals are greater than those occurring during the intermediate traversals. f

Alternative methods of obtaining a greater initial and final deflection are illustrated in Figures 3 and 4.

' In Figure 3, the desired additional deflection is obtained by providing additional pairs of deflecting electrodes I6, I1, and I8, I9, between the gun I and the electrodes 2, 3, and between the electrodes 2, 3, and the collecting electrode 6 respectively. An advantage' of this arrange- 75 each stream of electrons may la separate deflecting iield and impinge on the are used, being i 2. The method of 3 ment is that' the' potentialdifference or differences between the additional deilecting electrodes can be made greater than that between the main deflecting electrodes witho t reducing the delay Vobtained with a given size or the main deflectig electrodes. Alternatively,` the additional declosely spaced ilecting electrodes can be more than the main deilecting electrodes.

It will also be observed that in Figure 3 the reflecting electrodes 4 and 5 are more widely spaced from the deflecting electrodes 2 and 3 than is the case in Figure 1. It will be appreciated from the discussion above in connection with Figure 1 that since the distance d is increased the effect of. this arrangement is to increase greatly the delay obtainable in the device with a given potential difference' between the vdeiiecting electrodes.

Instead of providing additional deflecting means the main deiiecting electrodes can be provided with extensions as indicated at 20 in Figure 4 of the drawing. In this case also two pairs of main deflecting electrodes 2l, 22, and- 23, 2li, are provided, these electrodes, with their extensions 2B, being in the form) of L-shapedA plates. This arrangement may be convenient in `cases where very large delays are required.

By incorporating more than one source of electrons or by producing morethan one modu- -f' ,A i lated stream ofelectrons in a device according to the invention, for example, in the manner'.I described in the specification of co-pending United States applicationSerial No. 366,639, with refer;

ence to Figure 3 thereof, it is possible to employ 'such a device for mixing similar or diierent,

signals with varying delays. Further, if desired,

be passed through of magnetic force of a substantially homogeneous lelectromagnetic iield crossed at right angles by an electrostatic field, reflecting the electrons passing through the electrostatic iieldv t'o .repass them through the crossed fields, `and collecting the repassed electrons of the modulated beam of electrons.

producing a time delayed train of electrical signals which comprises the steps of producing a beam of electrons, modulating the produced beam of electrons by the train of electrical signals to be delayed, directing the modulated beamof electrons along the lines of magnetic force of a substantially homogeneous4 b electromagnetic eld crossed at right angles by anelectrostatic eld, reecting .the electrons passing through the electrostatic field to repass them through the crossed ilelds, collecting the repassed electrons of the trons,y and producing the collected electrons.

3. The method of producing a'time delayed train of electrical signals which comprises the steps of producing a beam'of electrons, modumodulated beam of eleclating the produced beam of electrons bythe train of electrical signals tcbe delayed, directing the modulated'beam of electrons along the lines a voltage proportional to.

of magnetic force of a substantially homogeneous electromagnetic field crossed at rightangles by an electrostatic field, repassing the beam of electrons through the crossed ilelds a plurality of times, subsequently ,collecting the repassed electrons of the modulated beam of electrons and regulating the number of passages by controlling the intensity of the electrostatic field.v

4. Apparatus for producing a time delayed train of electrical signals which comprises means for\producing a beam of electrons, means for modulating the produced beam of electrons by the train of electrical signals to be delayed, means for directing the modulated beam of electrons along the lines of magnetic force of a substantially homogeneous electromagnetic ileld crossed at right angles by an electrostatic ileld, means for reflecting the modulated ybeam of electrons passing through thelelectrostatic eld to repass them through the crossed fields, and

means for collecting the repassed electrons of the modulated beam of electrons.

5. Apparatus for producing a time delayed train of electrical signals which comprises means for producing a 'beam of electrons, means for modulating the produced beam of electrons by the train of electrical signals to be delayed, means for directing the modulated beam of electrons along the lines of magnetic force of 'a substantially homogeneous electromagnetic ileld crossed at right angles by an electrostatic field, means for repassing the modulated beam of electrons through the crossed fields a plurality of times, means for subsequently collecting the repassed electrons of the modulated beam and means for regulating the number of passages by controlling the intensity of the electrostatic field.

6. Apparatus for producing a time delayed train of electrical signals comprising a pairlof parallelly opposed reflecting electrodes, means to produce a substantially homogeneous 'electromagnetic fleld perpendicular to and intermediate said reflecting electrodes, electrode means intermediate said reflecting electrodesand perpendicular thereof for producing an electrostatic field perpendicular to said electromagnetic field, means adjacent one of said reflecting electrodes to project a signal modulated beam of electrons along lines of magnetic force into said electromagnetic andelectrostatic elds, means adjacent the other of said reflecting electrodes to collect elec-i trons from said beam and means to produce a train of electrical signals proportional to the collected electrons.

7. Apparatus for producing a time delayed train of electrical signals comprising a pair of parallelly opposed reflecting electrodes, means `to produce a substantially homogeneous electromagnetic fleld perpendicular to and intermediate said reflecting electrodes, electrode means intermediate said reflecting electrodes and perpendicular thereof for producing an electrostatic ileld perpendicular to said electromagnetic eld, means adjacent one of said reilecting electrodes to project a signal modulated beam of electrons along lines of magnetic force into said electromagnetic and electrostatic fields, means adjacent the other of said reflecting electrodes to collect electrons from said beam, mean-s to produce a train of electrical signals proportional to the collected electrons, and means intermediate said projecting means and said electrostatic means and between said electrostatic electrode means and said collecting means to produce deflections of the signal modulated beam.

8. Apparatus for producing a time delayed train of electrical signals comprising a pair of parallelly-opposed reflecting electrodes, means to produce a substantially homogeneous electromagnetic ileld perpendicular to and intermediate said reflecting electrodes, L-shaped electrode means intermediate said reflecting electrodes and perpendicular thereof for producing an electrostatic ileld perpendicular to said electromagnetic field, means adjacent one of said reflecting electrodes to project a signal modulated beam of electrons along lines of magnetic force into said electromagnetic and electrostatic fields, means adjacent the other of said reflecting electrodes to collect electrons from said beamand means to produce a train of electrical signals proportional to the collected electrons.

9. Apparatus for producing a time delayed train of electrical signals comprising a pair of parallelly opposed reflecting electrodes, means to produce a substantially homogeneous electromagnetic eld perpendicular to and intermediate said reflecting electrodes, a plurality of pairs of L-shaped electrode means intermediate said reilecting electrodes and perpendicular thereof for producing an electrostatic leld perpendicular to said electromagnetic leld, means adjacent one of said reflecting electrodes to project a signal modulated beam of electrons along lines of magnetic force into said electromagnetic and electrostatic fields, means adjacentthe other of said reflecting 'electrodes to collect-electrons from said beam and means to produce a train of electrical signals proportional to the collected electrons.

10. Apparatus for producing a time delayed vtrain of electrical signals comprising a pair of parallelly opposed reflecting electrodes, means to produce a substantially homogeneous electromagnetic fleld perpendicular to and intermediate said reflecting electrodes, electrodel means inter- .mediate said reflecting electrodes and perpendicular thereof for producing a non-uniform electrostaticveld perpendicular to said electromagnetic ileld, means adjacent one of said reflecting electrodes to project a signal modulated beam of electrons along lines of magnetic force into said electromagnetic and electrostatic iields, means adjacent the other of said reflecting electrodes to collect electrons from said beam and means to produce a train of electrical signals proportional to the collected electrons.

GEORGE STANLEY PERCIVAL FREEMAN. 

